Phys 101 Alanna Houston
November 13, 2007
- Example: The voice of a person who has inhaled Helium sounds
very high pitched. Why?
o Look at wave equation. Velocity increases by three and the
frequency increases because the wavelength remains
- Example: At 20 degrees C, (take v = 343 m/s), how long an organ
pipe do you need for fundamental to be 294 Hz?
o 294 = (2)(343/L)
o L = 0.58 m
- Example: An organ pipe resonates at 264 Hz. 440 Hz, and 616 Hz
but not at any frequencies in between. Is it an open or a closed
o Closed pipe. This is because there is a gap of 176, and then
if you subtract 176 from 276, you get 88, which is not the
other. Half of step between harmonics.
o What is the fundamental frequency? 88 Hz
- Sound waves come together to form interference
- Spatial interference (same region) can happen constructively or
- Usually only specific wavelengths can interfere destructively
- Interference can also happen in time such as in beats where there
are two waves of similar frequency but not the same frequency. Phys 101 Alanna Houston
- The beat frequency is the difference between the original
- Example: Two violin strings are set to 294 H